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Full text of "Handbook Of Chemical Engineering - I"

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discharge valves and the suction head from there to the water level in the supply tank. A suction head of 12 ft. is sufficient for any temperature at the sea level, because water can not exist at a temperature above 212°F. except under pressure, the effect of which is added to the static head. The broken lines parallel to a indicate the lifts attainable or heads required at various altitudes.
212° 200 Eft Q   150	S Altitude S   lo																											
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				\	\	\	\	^	^^	\		\j									S^-	^						
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Temperature. § 1								N^	C*	^	^	\	s;		s,	S,									\			£
									svk	s,	x^	v^	k	*s			\								\			
										\	\	\	\	\	S			\								\		3
											\	\	k,	\	\	^			^	.								
												\	\	\	\	V		^									i	
													\	\	\	\	s		s		^						\	
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															s	\	s	^	s s		\		s					
	0                  10                   0                    10                   20                   30 Su.cfcion Head                              Suction Lift, .Feet																											
FIG. 31.—Suction lifts and head diagram.
To dispose of the exhaust steam it may be run into the suction pipe where it mixes with the water and is condensed. This method is especially recommended in connection with a mine sinking pump, as it makes the unit self contained. The exhaust pipe is provided with a three-way cock, so that the exhaust can be turned into the atmosphere for starting. A good construction for a suction condenser is to allow the steam to enter an annular space around the suction pipe, to travel upward and enter the suction pipe near the top, where it condenses without causing any disturbance (Fig. 32). The water may be heated thereby 20°.
The exhaust of a pump may also be disposed of by a jet condenser usually equipped with a single direct-acting wet vacuum pump, the object of which is to remove the condensate, the injection water and the air from the tail end of the condenser. The injection water is drawn into the condenser cone from the suction well and is discharged into the sewer by the wet vacuum pump.
By using a properly proportioned condensing pump in place of a non-condensing pump a saving of from 30 to 40 per cent in steam may be effected. Tests investigating the same pump, running condensing and non-condensing, show the gain in power rather than the saving in steam, because in order to develop the same power the steam supply must be cut down when running condcns-FIG. 32.—Suction condenser. ing and the enSme is "then running under unfavorable
conditions for which it was not designed.
Surface condensers have less moving machinery and use less steam for operating than jet condensers, but are liable to be out of service a longer time while the tubes are